A novel type of adsorbent (CM) was synthesized by cellulose modified with maleic anhydride to remove heavy metal ions and organic dyes in this work. The synthesized adsorbent was characterized by FTIR, SEM, TGA and XRD. The degree of carboxyl group of CM was found to be 2.7 mmol g(-1) by the titration method. The adsorption of Hg(II) ions as heavy metal ions while basic fuchsine, methylene blue and crystal violet as organic dyes by CM was investigated. The influence of different experimental parameters such as pH, contact time, temperature on removal process was evaluated. The results indicated that the CM has a good adsorption capacity for Hg(II). The maximum adsorption capacity of Hg(II) was found to be 172.5 mg g(-1), and the adsorption process was described by Freundlich isotherm model of adsorption well. The process of basic fuchsine, methylene blue and crystal violet adsorbed by CM was also studied and the adsorption removal rate of those organic dyes was 88.10, 98.47 and 92.85 % under the optimum conditions, respectively. The adsorption process was depicted by the Langmuir isotherm model more correctly.